Subgingival microflora and periodontal disease

The development and in vitro evaluation of acrylic strips and dialysis tubing for local drug delivery

This study reports on the development of drug containing acrylic strips for delivering antimicrobial agents and compares the in vitro release pattern with dialysis tubing. Polyethylmethacrylic strips of suitable dimensions containing 10 to 50% chlorhexidine acetate, 40% metronidazole and 40% tetracycline were prepared. Daily release of the incorporated drugs into 1 ml aliquots was measured spectrophotometrically over a 14 day period. Similarly the release of chlorhexidine gluconate from various lengths of patent and heat sealed dialysis tubing was recorded for 4 days. At 30%, 40% and 50% admixtures the acrylic strips released chlorhexidine up to the 14 day period and a parallel bioassay confirmed the maintenance of antibacterial activity to this time. At the same admixture the release of metronidazole was greater than chlorhexidine and tetracycline. All drugs were released at high levels on day 1 followed by a marked fall in release by day 2 and progressive fall thereafter. The release from tubing was almost total within 24 hours and was independent of sealing the ends. The strips appear to have potential for prolonged drug delivery to periodontal pockets. Preliminary clinical use revealed no patient acceptability problems and alterations in subgingival flora were produced.

Bacterial variability within diseases periodontal sites

The purpose of this study was to examine the variability in bacterial proportions between individual periodontal sites in patients with chronic periodontitis by means of differential dark-field microscopy. Fourteen patients with untreated, moderate to advanced disease were included. Probing depth, plaque and gingival index scores were recorded for each patient. Microbial samples were collected from the tooth surface with the greatest proving depth in each sextant and examined individually by dark-field microscopy. The results indicated that proportions of spirochetes and motile rods at any given probing depth varied considerably, ranging from those expected at healthy sites to those expected at diseased sites. In accordance with previous studies, mean percentages of spirochetes tended to vary directly with increased PD, PlI and GI scores, while mean percentages of coccoid cells tended to follow a reverse pattern. However, no significant correlations could be demonstrated when measurements from individual sites were analyzed. Most of the variance in the data was due to differences between subjects rather than differences between sites. It is postulated that the large variance between subjects and sites is due in part to the cyclical nature of the disease and to the lack of synchrony between remissions and exacerbations at different sites and in different patients.

The effect of short-term administration of minocycline HCl on gingival inflammation and subgingival microflora

The purpose of this investigation was to determine the efficacy of minocycline hydrochloride in the management of subgingival microorganisms and periodontal disease. In a double-blind, split-mouth study, minocycline or placebo was administered systemically for 7 days to 26 adults with moderate-to-serve periodontitis. Four study groups were examined: (i) minocycline-scaled, (ii) minocycline-unscaled, (iii) placebo-scaled, and (iv) placebo-unscaled. The minocycline-scaled group responded most favorably, with improved gingival health for at least 49 days and with marked reductions in total bacterial counts and proportions of spirochetes for at least 70 days (termination of the study). Minocycline administration with no periodontal scaling and root planing also resulted major, long-lasting shifts in the subgingival microflora. Scaling alone was least effective in changing the microflora. The data indicated that minocycline may be a useful adjunct in the treatment of periodontal disease. Further studies are needed, however, to determine the long-term effect of minocycline therapy on the periodontal attachment level.

Effect of Chinese and western antimicrobial agents on selected oral bacteria

The susceptibility of selected oral bacteria, including suspected periodontopathogens, to a commonly employed Chinese herbal medicine Huang-chin (HC, Scutellaria baicalensis) was tested in vitro. The minimum inhibitory concentration (MIC) and minimum bactericidal concentrations (MBC) were determined. HC was also compared with tetracycline, alexidine, and stannous fluoride. HC decoction, at a concentration of 2%, was bacteriostatic in eight of 11 bacteria tested, but a concentration of 3.13% or greater was required for bactericidal effect. Among the tested bacteria, Bacteroides melaninogenicus ss intermedius was the most sensitive (MIC = 1.57%, MBC = 2%); Actinomyces viscosus was the least sensitive (MIC = 6.25%, MBC = 12.5%). Tetracycline, alexidine, and SnF2 were bactericidal in vitro in all bacteria tested at concentrations lower than those used clinically.

Relationship between the percentage of subgingival spirochetes and the severity of periodontal disease

The purpose of this study was to determine the correlations between various clinical assessments of inflammatory periodontal disease and the percentage of motile bacteria in the subgingival flora of sites representing widely varying states of periodontal disease. Darkfield microscopy was used to determine the percentage of spirochetes and other motile bacteria at two sites from each of 60 volunteers. For each site the following clinical assessments were recorded: Plaque Index (PII), gingival exudate (GE), Gingival Index (GI), bleeding tendency (BT), pocket depth (PD), connective tissue attachment loss (AL) and Periodontal Disease Index (PDI). Statistically significant (P less than 0.001) positive correlations (r) were found between the percentage of subgingival spirochetes and PII (r=0.54), GE (r=0.61), GI (r=0.57), BT (r=0.59), PD (r=0.56), AL (r=0.56) and PDI (r=0.61). Clinically healthy sites harbored much lower percentages of motile bacteria than did clinically disease sites. Most of the observed variation in the percentage of motile bacteria could be accounted for by variations in the percentage of spirochetes. The most significant increases in the relative percentages of subgingival spirochetes occurred when bleeding upon probing was observed as a sign of inflammation and/or when pocket depth and attachment loss exceeded 3 mm.

Butyrate: a cytotoxin for Vero cells produced by Bacteroides gingivalis and Bacteroides asaccharolyticus

Culture filtrates of B. gingivalis and B. asaccharolyticus are cytotoxic for Vero cells. It is shown that the cytotoxic effect is due to the butyrate concentrations present in the culture filtrates of these strains. This cytotoxic effect proved to be reversible. Strains of the B. melaninogenicus subspecies intermedius and melaninogenicus did not produce butyrate and did not show cytotoxic activity towards Vero Cells. The significance of the production of toxic concentrations of butyrate for the etiology of especially periodontal diseases is discussed.

Differences in lymphoproliferative responses to the bacterium Actinomyces viscosus in various mammalian species

A water-soluble extract of Actinomyces viscosus (AVS) was tested for its capacity to induce DNA synthesis in lymphocytes from man, monkeys, mice and guinea pigs. The results indicated that the AVS induced an in-vitro lymphoproliferative response, as assessed by tritiated thymidine incorporation, in mouse-spleen cells, in the majority of human peripheral blood samples tested and in macaque monkey spleen cells. The AVS also elicited a blastogenic response from spleen, lymph node and peripheral blood lymphocytes from guinea pigs immunized with A. viscosus. The AVS did not elicit a lymphoproliferative response from human-cord blood cells, monkey peripheral blood lymphocytes, or peripheral blood and spleen lymphocytes from non-immunized guinea pigs. Thus there was a difference in the ability of A. viscosus to induce DNA synthesis in lymphocytes from the different animal species tested.

The development of an altered gingival crevicular microflora in the alloxan-diabetic rat

The microflora of the rat gingival crevice were examined at various time intervals after inducing experimental diabetes. A variety of Gram-positive and Gram-negative cocci and short rods were isolated from the normal rat crevice. Within a week after alloxan administration, Leptotrichia buccalis was detected for the first time. Other features in the diabetic animals included an increased frequency of isolation of Proteus spp., Lactobacillus spp. and decrease of Escherichia coli. Occasionally, a decrease was also observed in Bacteroides spp. and Streptococcus spp. No difference was observed between diabetic and non-diabetic animals in the isolation of Selonomonas, Campylobacter, Bifidobacterium and Actinomyces. Plaque accumulation was markedly increased in the diabetic rats. It was concluded that the change in gingival microflora resulted from diabetes-induced alterations in the sulcular environment (such as increased substrate levels, e.g. glucose and urea, and decreased oxygen) and that the microbiological changes preceded the depending of the periodontal pocket.

API ZYM system for identification of Bacteroides spp., Capnocytophaga spp., and spirochetes of oral origin

A total of 80 oral strains of Bacteroides gingivalis, B. asaccharolyticus, B. melaninogenicus subsp. intermedius, B. melaninogenicus subsp. melaninogenicus, Capnocytophaga, Treponema denticola, and T. vincentii were characterized with the API ZYM system for 19 enzyme activities. Comparison of anaerobic and aerobic incubation with nine reference strains of these organisms showed no important differences. The key differential tests for black-pigmented Bacteroides strains and treponemes of oral origin were trypsin, alpha-glucosidase, and N-acetyl-beta-glucosaminidase. All Capnocytophaga strains produced distinctive aminopeptidase activities but varied in their glycosidic capabilities. The presence of a trypsin-like activity in B. gingivalis, T. denticola, and a group of Capnocytophaga strains may contribute to tissue destruction in periodontal disease.

The effect of female sex hormones on subgingival plaque

The periodontal status of three groups of women; pregnant, taking oral contraceptives, and nonpregnant, were evaluated clinically and microbiologically for changes in their gingiva and any corresponding changes in the subgingival microbial plaque, specifically the percentage of Fusobacterium species and Bacteroides species. Overall, the women had relatively good gingival health. However, statistically significant increased scores were observed in the Gingival Index and the gingival crevicular fluid flow in the pregnant group compared with the nonpregnant group. The most dramatic microbial changes were the increased proportions of Bacteroides species both in the pregnant group and the group taking oral contraceptives over the nonpregnant group. Increased female sex hormones substituting for the napthaquinone requirement of certain Bacteroides were most likely responsible for this increase. No statistically significant clinical difference was noted between the group taking oral contraceptives and the nonpregnant group, although a 16-fold increase in Bacteroides species was observed in the group taking oral contraceptives.

Polyclonal B-cell activation induced by extracts of Gram-negative bacteria isolated from periodontally diseased sites

The objective of this research was to determine whether gram-negative bacteria frequently isolated from periodontally diseased sites contained polyclonal B-cell activators. Polyclonal B-cell activation, which results in nonspecific activation of multiple B-cell clones was analyzed by a hemolysis-in-gel assay designed to detect a broad range of antibody specificities. Extracts from numerous bacterial strains, including Bacteroides gingivalis, Bacteroides melaninogenicus subsp. melaninogenicus, B. melaninogenicus subsp. intermedius, Fusobacterium nucleatum, Selenomonas sputigena, Capnocytophaga ochracea, and Actinobacillus actinomycetemcomitans, were tested. Extracts of the above organisms were found to stimulate polyclonal antibody responses in cultures of normal human peripheral blood lymphocytes, although the magnitude of stimulation varied among the extracts. Optimal antibody-forming cell responses were found at stimulator doses between 5 and 1,000 micrograms/ml. We conclude that the resident gram-negative subgingival flora associated with periodontal lesions possesses potent polyclonal B-cell activators. These activators may contribute to disease pathogenesis by inducing B lymphocytes to produce antibody, osteolytic factors, or both and possibly other mediators of inflammation.

Role of surface fimbriae (fibrils) in the adsorption of Actinomyces species to saliva-treated hydroxyapatite surfaces

We studied the adsorption, morphological, and serological characteristics of selected Actinomyces and related species. Evaluation of uranyl acetate-stained cells by electron microscopy revealed wide variations among strains in the frequency of surface fimbriae. These variations did not always correlate with the percent adsorption to saliva-treated hydroxyapatite of the various Actinomyces strains. However, two strains of Rothia dentocariosa possessing no surface fimbriae and five strains of A. israelii possessing very few surface fimbriae exhibited feeble adsorption to saliva-treated hydroxyapatite. Although the calculated number of adsorption sites on saliva-treated hydroxypatite did not vary widely among the strains tested, significant differences were observed in the affinities calculated for some species or serotypes. The mean affinities for strains of A. viscosus serotype 2 and A. naeslundii serotype 3 were similar, and these strains adsorbed well to saliva-treated hydroxyapatite. The mean adsorption and affinity for the A. naeslundii strain serotype 1 and all strains of A. israelii tested were significantly less than those determined for the A. viscosus serotype 2 or A. naeslundii serotype 3 strains. Adsorption inhibition activity of antiserum to strain T14V, previously shown to be solely related to antibodies in immune serum directed against the VA1 fimbria (fibril) antigen, was removed by preadsorption of the antiserum with most A. viscosus and A. naelundii strains, but not with A. israelii strains. This suggests some cross-reactivity among strains of A. viscosus and A. naeslundii but not A. israelii. Adsorption to saliva-treated hydroxyapatite of all A. viscosus and A. naeslundii strains tested was strongly inhibited by fimbriae isolated from A. viscosus strain T14V. Collectively, these data suggest that the adsorption of certain A. viscosus and A. naeslundii strains is mediated by surface fimbriae, many of which appear serologically cross-reactive with strain T14V fimbriae.

Enzymatic characterization of some oral and nonoral gram-negative bacteria with the API ZYM system

The API ZYM system (Analytab Products, Plainview, N.Y.), containing 19 chromogenic substrates, was utilized semiquantitatively to detect extracellular acid and alkaline phosphatases, aminopeptidases, proteases, esterase-lipase, phosphoamidase, and glycosidases in 128 oral and nonoral isolates of black-pigmented Bacteroides, Actinobacillus, Haemophilus aphrophilus, Capnocytophaga, Fusobacterium nucleatum, Wolinella recta, and Veillonella parvula. In the black-pigmented Bacteroides group of organisms, a strong trypsin reaction was present in Bacteroides gingivalis (oral species) but not in Bacteroides asaccharolyticus (nonoral species). Bacteroides melaninogenicus subsp. melaninogenicus, in contrast to Bacteroides melaninogenicus subsp. intermedius, exhibited strong N-acetyl-beta-glucosaminidase activity. H. aphrophilus produced beta-galactosidase and alpha-glucosidase, but the closely related Actinobacillus actinomycetemcomitans did not. Capnocytophaga was distinct with respect to strong aminopeptidase reactions. This study showed that a wide range of enzymes which have the potential of causing tissue injury and inflammation can be elaborated from major oral gram-negative species. Also, the API ZYM system appears to be a valuable adjunct to traditional biochemical testing in identifying oral gram-negative species.

Serum neutralizing activity against Actinobacillus actinomycetemcomitans leukotoxin in juvenile periodontitis

A relatively high incidence of infection by Actinobacillus actionomycetemcomitans can be shown in subgingival plaque samples obtained from patients with juvenile periodontitis. These organisms possess a potent leukotoxin(s) which rapidly destroys isolated human polymorphonuclear leukocytes (PMNs) and monocytes. If such leukotoxins operate in vivo, they could deprive the gingival crevice area of an essential antibacterial defense mechanism. We have found that sera from juvenile periodontitis patients consistently (greater than 90%) contain antibodies which neutralize Actinobacillus actinomycetemcomitans leukotoxin(s). On the other hand, sera from normal individuals or patients with other types of periodontal disease usually amplified rather than inhibited the leukotoxic reaction. Many patients with juvenile periodontitis have demonstrable defects in PMN or monocyte chemotaxis and this may place them at risk to gingival infection by Actinobacillus actinomycetemcomitans. The immune response against these organisms could be a crucial determinant in the course of juvenile periodontitis. While this disease is relatively rare, it does cause immeasurable emotional, physical and economic hardship for patients and their families. The identification of Actinobacillus actinomycetemcomitans as a potential pathogen in this disorder may eventually lead to specific forms of therapy to prevent and eliminate infection by this organism in these patients.

Black-pigmented Bacteroides spp. in the human oral cavity

Five healthy children under 6 years of age, five healthy adults, and 10 adult periodontitis patients were examined for the prevalence and distribution of black-pigmented Bacteroides in the oral cavity. A total of 13 samples was obtained from each individual, including four supragingival and four subgingival dental plaques, dental occlusal surface, buccal mucosa, dorsal tongue, tonsil, and whole saliva. Black-pigmented Bacteroides were recovered from nine adult periodontitis patients. Healthy adults harbored the organisms in low incidence and proportions, whereas the children exhibited no cultivable black-pigmented Bacteroides. The organisms were isolated in highest proportions from dental plaque, especially subgingival plaque, and from the tonsil area, indicating that these sites constitute the organisms' primary ecological niche in the oral cavity. The predominant isolate was Bacteroides melaninogenicus subsp. intermedius followed by Bacteroides gingivalis and B. melaninogenicus subsp. melaninogenicus. B. melaninogenicus subsp. levii constituted low proportions of supragingival microflora of one adult periodontitis patient. A positive correlation was demonstrated between the proportion of black-pigmented Bacteroides (mainly B. melaninogenicus subsp. intermedius) and both the severity of gingival inflammation and the periodontal pocket depth, suggesting that these organisms may contribute to the pathogenesis of certain forms of periodontal disease.

Complement-dependent histamine release from rat peritoneal mast cells, induced by lipopolysaccharides from Bacteroides oralis, Fusobacterium nucleatum and Veillonella parvula

The capacity of phenol/water extracted lipopolysaccharides (LPS) from Bacteroides, Fusobacterium and Veillonella to induce histamine release from rat peritoneal mast cells has been evaluated by means of a bioassay using atropinized guinea pig ileum and a fluorescence assay. Histamine release was found to be completely complement dependent. It was also found that LPS of Veillonella have the greatest capacity to induce histamine release and Bacteroides have the weakest.

An experimentally induced phlegmonous abscess by a strain of Bacteroides gingivalis in guinea pigs and mice

The virulence of B. gingivalis strain W83 was studied in an experimental animal model. Cells grown overnight, washed and resuspended in broth, were injected intradermally or subcutaneously in the back of guinea pigs, rats and mice. This strain proved to be very virulent, causing a severe phlegmonous abscess in guinea pigs. Also in mice, which are thought to be resistant to infections with black-pigmented Bacteroides strains, the same type of infection could be induced. Rats proved to be rather insensitive. The model presented can be used as a simple virulence test for these anaerobic bacteria.

Tetracycline in the treatment of periodontal disease: review of current literature

For many years, tetracycline has been prescribed in the treatment of periodontal disease with little research data supporting such use. Current data suggest that most patients with periodontal disease are best treated by conventional techniques of subgingival debridement.

Actinobacillus actinomycetemcomitans in human periodontal disease: a cross-sectional microbiological investigation

Actinobacillus actinomycetemcomitans is a facultative gram-negative bacterium which has been associated with severe oral and nonoral infections. This study examined its occurrence in the oral cavities of 10 normal juveniles, 11 normal adults, 10 juvenile periodontitis patients, and 12 adult periodontitis patients. Four deep periodontal pockets and two normal periodontal sites were sampled in the diseased patients, and six normal periodontal sites were sampled in the healthy individuals. In all subjects samples were obtained from the cheek, tongue, and saliva. Samples from a total of 172 normal periodontal sites, 83 deep periodontal pockets, 42 cheek mucosae, 42 tongue dorsa, and 42 salivas were examined. Isolation was performed by using a medium for selective isolation of A. actinomycetemcomitans (Trypticase soy agar [BBL Microbiology Systems] supplemented with 10% serum and 75 mug of bacitracin per ml). The carrier rates were 20% for normal juveniles, 36% for normal adults, 50% for adult periodontitis patients, and 90% for juvenile periodontitis patients. A. actinomycetemcomitans was on average recovered in about fivefold-higher numbers from infected deep periodontal pockets than from infected normal subgingival areas. Samples of periodontal pockets generally contained 100-fold-more cells of A. actinomycetemcomitans than did samples of the cheek, tongue, and saliva. A. actinomycetemcomitans is commonly isolated from patients with juvenile periodontitis, often isolated from patients with adult periodontitis, and occasionally isolated from normal juveniles and adults. Its primary oral ecological niche appears to be dental plaque and periodontal pockets.

Energy metabolism in Capnocytophaga ochracea

Among the microflora of the gingival sulcus are members of the genus Capnocytophaga which have been implicated as possible etiological agents of juvenile periodontitis and systemic infectious diseases. In this study, the pathway used by C. ochracea strain 25 for generating energy from glucose was investigated. When grown in a complex medium supplemented with glucose and NaHCO(3), the major end products formed were acetate (4.6 mmol), succinate (11.0 mmol), pyruvate (4.3 mmol), and oxalacetate (3.6 mmol), and the molar growth yield was 58. Addition of yeast extract to the growth medium caused (i) an increase in acetate (9.2 mmol) and succinate (14.3 mmol), (ii) a decrease in pyruvate (0 mmol) and oxalacetate (1.1 mmol), and (iii) the molar growth yield increased to 75. Glucose was transported by a phosphoenolpyruvate:phosphotransferase system and then catabolized to phosphoenolpyruvate by enzymes of the Embden-Meyerhof-Parnas pathway. No activities were detected for the key enzymes of the Warburg-Dickens, Entner-Douderoff, or hexose phosphoketolase pathways. During growth in the yeast extract-supplemented medium, approximately 37% of the phosphoenolpyruvate carbon was converted to acetate by pyruvate kinase, a pyruvate-decarboxylating enzyme activity, and acetate kinase; the remaining 63% was converted to succinate via phosphoenolpyruvate carboxykinase, malate dehydrogenase, fumarate hydratase, and fumarate reductase.

Antigenic studies of oral and nonoral black-pigmented Bacteroides strains

Antigens of several oral and nonoral strains of Bacteroides asaccharolyticus (proposed classification of oral B. asaccharolyticus, Bacteroides gingivalis), Bacteroides melaninogenicus subsp. intermedius, B. melaninogenicus subsp. melaninogenicus, and B. melaninogenicus subsp. levii were identified in soluble preparations obtained by sonication, autoclaving, and NaOH treatment of whole bacterial cells. The sonicate preparations contained the most complete representation of soluble antigens using antisera to the whole organism in gel precipitation tests. Among strains of B. melaninogenicus subsp. intermedius many common antigens were detected, and no consistent antigenic differences were seen between strains from oral and nonoral sites. None of the antigens of B. melaninogenicus subsp. intermedius reacted with sera raised to several strains of oral or nonoral B. asaccharolyticus, nor did antigens prepared from the latter strains react with antisera to B. melaninogenicus subsp. intermedius. At least one common antigen was shared by strains of B. melaninogenicus subsp. intermedius and strains of B. melaninogenicus subsp. melaninogenicus; however, subspecies-specific antigens were also found. Antigens from and antisera to oral and nonoral strains of B. asaccharolyticus did not react with sera to and antigens from B. melaninogenicus subsp. melaninogenicus. Strains of B. asaccharolyticus isolated from the oral cavity were antigenically distinct from strains of B. asaccharolyticus obtained from nonoral sites and lesions. This lack of cross-reactivity between the oral and nonoral strains of B. asaccharolyticus together with recent findings of marked genetic differences between oral and nonoral strains of B. asaccharolyticus suggest that these groups of organisms may represent different species.